Ancient Philosophy, in particular:

If these gel with your mind, you can venture further down the Hellenistic Philosophy route.

One of my key lessons from these works is that without a "framework" of life, you typically have to make un-principled decisions from the ground up. Philosophy of that time was really geared toward building a holistic framework for life.

Further to that, I would recommend Military Strategy as a useful topic— How do the best generals through history make exceptional decisions at the highest level, under maximum duress, at the highest stakes?:

Not only did these books help my decision making, but developed my ability to build multi-decade strategic thinking as a (ever improving) skillset.

Until a few years ago, I was not a very avid reader— I still have a long way to go, but I have been an obsessive self-learner since 11 or 12. There is wisdom in some old books that has been really profound to me.